As higher integration in semiconductor integrated circuits is pursued with increasing vigor, rapid progress has been made in the field of the technology for manufacturing multilayered semiconductor devices in recent years. It is necessary to form both trench wiring to connect elements arranged along the horizontal direction and via hole wiring to connect elements arranged along the vertical direction when manufacturing a semiconductor device with a multilayer structure. In recent years, copper is used as the wiring material and an organic low k material due to its low resistance and outstanding antielectro-migration characteristics such as SiLK™ (a product of Dow Chemical, U.S., hereafter referred to as SiLK), which assures a low dielectric constant is used as a layer insulating material in the manufacturing process to achieve faster integrated circuits.
A wiring pattern is formed with copper, with which a compound with a high vapor pressure cannot easily be formed, by adopting a so-called damascene structure with an embedded wiring achieved through metal CMP technology. In addition, semiconductor elements with a so-called dual damascene structure achieved by simultaneously forming trench wirings for connecting the individual elements arranged along the horizontal direction and via wirings for connecting the elements arranged along the vertical direction have become increasingly common recently.
When a via is formed at a trench formed in a layer insulating film constituted of an organic low k film in the dual damascene structure forming technology in the related art, so-called shoulder loss tends to occur readily over a junction region (a via edge portion) where the trench and a via form a junction. If wirings are formed with vias where such shoulder loss has occurred, the electric capacitance between adjacent via wirings increases, which gives rise to a problem in that the desired electrical characteristics cannot be assured.
An object of the present invention, which has been completed by addressing the problem of the dual damascene structure formation in the related art, is to provide a new and improved etching method that does not allow shoulder loss to occur readily at the shoulder of an organic low k film layer when, for instance, forming a via at a trench formed in the layer insulating film constituted of the organic low k film and thus, makes it possible to achieve a wiring structure in a desired shape and with desired dimensions when wirings are embedded through a subsequent process.